"Shingling" of ink drops to produce inkjet images is known in the prior art. In inkjet printers which produce binary colors (i.e., black/white), shingling is accomplished by causing the inkjet printhead to make at least two passes over a single swath of raster scan lines of print data. During a first scan, every other pixel site is masked and during a second scan, the complementary pixel sites are masked. Ink deposited during a first scan is thus placed at every other pixel site and is allowed to dry before ink is placed on adjacent pixel sites during the second scan.
Multi-level shingling is also known in the prior art. In such a shingling procedure, instead of firing one drop per pixel site, the inkjet printhead is enabled to fire plural drops at each pixel site. The number of overlapping drops (and their respective volumes) is dependent upon the number of drops, one on top of each other, that can be accommodated while still retaining a desired level of image quality. Such a print technique is termed "drop-on-drop". Multi-level shingling is utilized to enable the deposition of various thicknesses of colored inks to achieve a desired level of color intensity.
Currently, inkjet printers have the capability of producing high quality images. Such printers utilize a printhead (e.g. whose nozzle plate 10 is as schematically shown in FIG. 1) which is capable of depositing four separate color dots, i.e., cyan (C), magenta (M), yellow (Y) and black (K). Nozzle plate 10 includes at least four columns of nozzles 11, 12, 13 and 14, with each column having N nozzles devoted to the deposition of a single color. The number of nozzles in each column defines the width of a swath of pixel sites that can be printed during a scan of the printhead across a media sheet. Further, there may be plural columns of nozzles devoted to each color.
Prior art printheads, of the type shown in FIG. 1, are controlled such that, as each column of nozzles arrives over a pixel position, in the sequence of nozzles shown, a respective nozzle is energized to deposit a color dot of ink. Such multi-color printheads have only been enabled to deposit a single dot per pixel site, with the deposition occurring in the order in which the color nozzles are arranged across nozzle plate 10. Thus, as shown in FIG. 1, if the scan direction is as shown by arrow 15, a magenta ink dot is invariably deposited before a cyan dot is deposited. Such invariant ordering of dot placement, at times, results in image artifacts and variations from a desired color representation.
It is known that both temporal and spatial shingling can improve image representations that are produced by an inkjet printhead (e.g., improved gray level representation and half-toning). Further, as above indicated, experience has shown that if the deposition of colors onto a media sheet is restricted to a certain order of color dots, undesirable image artifacts can be created (e.g., banding). Finally, there is a requirement to improve the image reproduction capability of inkjet printers to enable image representations to be produced that are closer to high quality photographic reproductions.
Accordingly, it is an object of this invention to provide an improved method and apparatus for controlling a multicolor inkjet printer.
It is a further object of this invention to provide an improved method and apparatus for controlling a multicolor inkjet printhead, wherein either temporally or spatially shingled images are produced.
It is yet another object of this invention to provide an improved method and apparatus for control of a multicolor inkjet printhead, wherein the sequence of deposition of colored dots is selectively alterable.
It is still another object of this invention to provide a method and apparatus for control of a multicolor inkjet printhead which reduces image artifacts in a resultant printed image.